Supported catalyst regeneration

ABSTRACT

There is provided a process for renewing the activity of used, supported metal catalysts for the hydrogenation of carbon monoxide to form a mixture of hydrocarbons comprising decreasing the hydrocarbon content of the catalyst, impregnating said catalyst under an non-oxidative atmosphere with a solution at least one weak organic acid, preferably a mono- or di-carboxylic acid, to the point where it has absorbed a volume of said solution equal to at least about 10% of its calculated pore volume, oxidizing the catalyst with a gaseous oxidant in the presence of the impregnating solution and activating the catalyst by reduction with hydrogen at elevated temperatures. Optionally, the catalyst is calcined after the oxidation step, and passivated after the activation step. A preferred means of decreasing the hydrocarbon content of the catalyst is contacting it with a hydrogen-containing gas at elevated temperatures.

RELATED APPLICATIONS

[0001] The assignee of this application is filing herewith the followingapplications: Docket No. 37227, entitled “Fischer-Tropsch CatalystEnhancement” Docket No. 37229, entitled “Supported Catalyst Activation”;Docket No. 39158, entitled “Supported Catalyst Treatment”; Docket No.39773, entitled “Catalyst Enhancement”; and Docket No. 39774, entitled“Catalyst Regeneration”. Also related in pending application Ser. No.09/628,047, filed Aug. 1, 2000, entitled “process for Increasing CobaltCatalyst Hydrogenation Activity Via Aqueous Low Temperature Oxidation”.

[0002] This invention relates to the production of higher hydrocarbonsfrom synthesis gas utilizing a supported metal catalyst, particularly acobalt catalyst.

BACKGROUND OF THE INVENTION

[0003] The conversion of synthesis gas, i.e. carbon monoxide andhydrogen, to higher value products is well known and has been incommercial use for many years. Typical processes include, for example,methanol syntheses, higher alcohol synthesis, hydroformylation andFischer-Tropsch synthesis. The synthesis gas mixture is contacted with asuitable catalyst typically comprising at least one Group VIII metals.Suitable Fischer-Tropsch catalysts comprise one or more catalytic GroupVIII metals, such as iron, cobalt and nickel. For oxygenate synthesis,copper may be included as well.

[0004] There exist many variations of the formulation and preparation ofcatalysts useful for the conversion of synthesis gas. In general, thecatalysts are classified into two broad types, unsupported metals, knownas Dispersed Active Metals and a larger groups of catalysts metalssupported on refractory oxides, such as silica, alumina, titania ormixtures thereof. Such catalysts, whether supported or unsupported maybe enhanced by the addition of other metals or metal oxides, known aspromoter metals.

[0005] Supports for catalyst metals are generally pilled, pelleted,beaded, extruded, spray-dried or sieved materials. There are manymethodologies reported in the literature for the preparation ofsupported catalyst metals. Examples of such techniques include incipientwetness impregnation, slurry impregnation, coprecipitation, and thelike. It will be appreciated that high metal loadings are generallyobtained by coprecipitation or multiple, i.e. two or three,impregnations, whereas low metal loading catalysts may be preparedutilizing a single impregnation. The catalyst metal content of suchcatalysts may vary from one to fifty weight percent. Promoter metals ormetal oxides may be added during the impregnation steps using solublesalts of the respective metals such as Pt, Pd, Rh, Ru, Os, Ir, Mo, W,Cu, Si, Cr, Ti, Mg, Mn, Zr, Hf, Al, Th and the like. It will further beappreciated that the choice of a particular metal combination and theamount thereof to be utilized will depend upon the specific applicationused in the conversion of synthesis gas. When a suitable support hasbeen impregnated with one or more metals as by impregnation to form acatalyst precursor, it may be dried and then calcined in anoxygen-containing environment. The precursor is thereafter activated byreduction at elevated temperature in the presence of a reducing gas,typically containing hydrogen. Optionally, the catalyst is activated bycontacting with hydrogen gas in presence of liquid hydrocarbons asdisclosed in U.S. Pat. No. 5,292,705.

[0006] Regardless of the particular formulation and method ofpreparation, all catalysts lose productivity and/or selectivity in use.Selectivity may vary with the particular synthesis, but is generallyexpressed in terms of the percent of an undesirable substance in theproduct mix. For example, methane selectivity in a Fischer-Tropschreaction is the percent of methane formed with the desired higherhydrocarbons. Degradation of the catalyst productivity may be due to anumber of phenomena including, without limitation, contamination bycatalytic poisons, deposition of carbonaceous residues, sintering, phasetransformation of the metal or metals and the like. U.S. Pat. No.5,283,216 discloses a method for rejuvenating an hydrocarbon synthesiscatalyst, which has been subjected to reversible, partial deactivationin a slurry synthesis process by contacting the catalyst with hydrogenat elevated temperatures in presence of liquid hydrocarbons. However,not all deactivated catalysts are rejuvenable. It is commerciallysignificant to extend the useful life of a used catalyst by varioustreatment procedures, for example, by means of regeneration.

[0007] There are catalyst regeneration methods described in theliterature. Typically, these techniques rely on contacting the usedcatalyst at elevated temperature with an oxygen-containing gas and/orsteam. Such treatment may be used to remove carbonaceous deposits andpoisons additionally converting the metal to its corresponding oxide oroxides. The regenerated catalyst is thereafter reactivated by means of areduction with a hydrogen-containing gas at elevated temperatures. Sucha treatment is described, for example, in U.S. Pat. No. 4,399,234.

[0008] U.S. Pat. No. 2,369,956 discloses a method for regeneration of aFischer-Tropsch catalyst wherein the catalyst is dissolved andsubsequently restored by re-precipitation of the catalytic metals. Itwas noted, however, that there were deposits remaining in the contactsubstance that materially increased the difficulty of restoring thecatalyst. An example of such substances is the high molecular weightparaffins from the used catalyst that make it difficult to filter themetal salt produced by dissolution of the catalyst with acid. Sincethese materials make purification of the salt difficult, it is taught inthe patent that hydrocarbon deposits on the catalyst must be initiallyremoved by treatment with flowing hydrogen at elevated temperatures. Theprocess of dissolution and re-precipitation may then be carried out. Itis also taught in the patent that the pyrophoricity of the treatedcatalyst might be mitigated by treatment with steam prior to dissolutionwith strong acid. However, there is nothing in the patent regarding theefficiency of the disclosed process, or the effect of exposing acatalyst support, such as described above, with strong acid.

[0009] U.S. Pat. No. 3,256,205 discloses a method of catalystregeneration by treatment with a strong acid to the point of incipientwetness of the catalyst prior to removal of carbonaceous depositsaccumulated during the catalytic cycle. It is specifically stated thatremoval of the carbonaceous deposits is detrimental in that the catalystsupport would be damaged by contact with the strong acid utilized.Suitable acids are stated as having a dissociation constant greater that10⁻² and are added to the catalyst in an amount varying from 0.5stoichiometry to the stochiometry required to form the salts of themetals present in the catalyst.

[0010] Khodakov et al. In a paper in Oil & Gas Science and TechnologyRev. IFP, 54, 525 (1999) teach that contacting a reduced cobalt catalystwith water, followed by drying and calcining in air results in theformation of smaller cobalt oxide crystallites relative to those thatwould be formed by decomposition of the initial cobalt salts. There isneither teaching nor suggestion that the disclosed methodology mighthave any application to catalyst regeneration.

[0011] It is clear from the foregoing discussion that there is not aclear incentive in the art to utilize any particular methodology inattempting to improve on the process of catalyst regeneration. In fact,the two patents discussed above would appear to negate each other sincethe first teaches that it is necessary to remove the carbonaceousdeposits from the catalyst prior to treatment with acid, yet the secondteaches that the carbonaceous deposits are necessary to prevent the acidfrom attacking the support structure. It also must be considered that itis generally not possible to use an aqueous-based solvent on a catalystcontaining a waxy hydrocarbon deposit because it is hydrophobic astypically observed with Fischer-Tropsch catalysts. Hence, it wouldappear that the process of the second patent would not haveapplicability to a Fischer-Tropsch catalyst since a characteristic ofthe process is that the pores of the used catalyst are filled with waxthat prevents good wetting by aqueous treatment solutions.

[0012] In hydroprocessing and oxidation catalysts, carbonaceous depositsare typically removed by calcination with an oxygen-containing gas atelevated temperatures. During such treatments, the metal-containingactive phase of the catalyst is converted to oxides. To further improvethe recovery of catalytic activity, contaminating metals are thenremoved by treatment with a basic solution, particularly one containingammonium carbonate or sodium cyanide. Such treatments are illustrated,for example, in U.S. Pat. No. 4,795,726 and German Patent DE 43 02 992.

[0013] The modifying of hydroprocessing catalysts is taught, forexample, in U.S. Pat. No. 5,438,028 wherein a finished catalyst isenhanced by the addition of a modifying agent in solution after whichthe catalyst is dried and optionally heated to a temperature of from120° C. to about 1000° C. The process does not include a final reductionstep to reactivate the catalyst. The modifiers disclosed in columnthree, with the exception of boron, which is not a metallic element, areall recognized poisons for Fischer-Tropsch catalysts. U.S. Pat. No.5,389,502 discloses application of the same process for the enhancing ofa hydroprocessing catalyst that has been regenerated by an oxidativetreatment. The application of the modifying agent to the surface of thecatalyst may be carried out to the point of incipient wetness. In bothof these patents, the preferred modifying agent is boron.

[0014] U.S. Pat. No. 6,201,030 discloses a process and apparatus forregenerating a particulate catalyst during operation of a reactor. Theprocess consists of withdrawing a partially spent catalyst as a slurryfrom a reactor to one of two regeneration stations, operating inparallel, treating the slurry with hydrogen and returning it to thereactor. The two regenerating stations are utilized in the alternativeoperating out of phase thereby facilitating continuous withdrawal andreturn of the slurry without substantial change in the liquid levelwithin the reactor. The disclosed process effectively fails to provideany means of regenerating severely deactivated catalyst or of improvingprocess reliability, such as by removing fines that may have formed inthe turbulent environment of the reactor.

[0015] It is generally recognized that the economic worth of a givencatalyst is a function of its original cost, its activity itsregenerability and its value as a used catalyst, e.g. for metalsrecovery. It is apparent from the foregoing discussion that there hasbeen considerable effort going back over many years to improve theeconomic worth of catalysts, since a process that will effectivelyincrease the value of a catalyst and/or extend the useful life thereofbefore it must be disposed of through conventional metal recovery willsignificantly improve the worth of that catalyst. Effective catalystregeneration effected while at the same time maintaining the reliabilityof the process requires the use of specific apparatus or combinations ofspecialized pieces of apparatus in combination with specific treatmenttechniques. Such process techniques and apparatus for carrying them outare provided in accordance with the present invention.

SUMMARY OF THE INVENTION

[0016] In accordance with the present invention, there is provided asignificant improvement in the catalytic hydrogenation of carbonmonoxide to form a mixture of hydrocarbons wherein the catalyst is asupported Fischer-Tropsch metal catalyst. The useful life of suchcatalysts is extended by a process of treating used catalyst comprising:decreasing the hydrocarbon content thereof, impregnating in the presenceof a non-oxidative atmosphere with a solution of one or more weakorganic acids, oxidizing in the presence of the impregnating solution atlow temperatures and forming an active catalyst by reducing with ahydrogen-containing gas at elevated temperatures.

[0017] Optionally, the catalyst is calcined in the presence of anoxidant-containing gas prior to activation. The activated catalyst mayalso be passivated. In addition, the catalyst may be initially reduced,such as by treatment with a hydrogen-containing gas prior to theimpregnation step described above. Reduction is beneficial to eliminatecertain impurities and to maximize the amount of catalyst metal in thelowest, or zero, oxidation state. Advantageously, the reduction may becarried out simultaneously with the reduction of hydrocarbons sincetreatment with a hydrogen-containing gas is one technique for reducingthe hydrocarbon content, i.e. dewaxing, the catalyst.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Supported metal catalysts, which correspond essentially toreduced metals formed by one of the recognized techniques discussedabove onto a suitable support structure, typically a refractoryinorganic oxide, such as titania, silica, silica-alumina, aluminum andthe like, are utilized in a broad range of applications such ashydrogenation of hydrocarbons and carbon monoxide. Titania is apreferred support material for the catalyst metal substrates treated inaccordance with the present invention. Start-up procedures for suchreactions, which may include specific activation sequences, are highlydependent upon the catalytic reaction, the process design and, inparticular, the reaction vessel design and configuration. The slurrybubble column reactor, is a preferred vessel for carrying out carbonmonoxide hydrogenation reactions. The use of slurry bubble column for COhydrogenation is particularly convenient in combination with thecatalyst regeneration process of the present invention. In suchreactors, the solid phase catalyst is dispersed or held in suspension ina liquid hydrocarbon phase by a gas phase, which continuously bubblesthrough the liquid phase. Supported catalysts useful for suchapplications contain at least 5 wt. %, preferably from 10 to 50 wt. %,of the catalyst metal in the reduced metallic form. Preferably, thecatalyst comprises one or more of Co, Ni, Cu, Ru, Rh, Pd, Os, Ir, Re andPt.

[0019] In the carbon monoxide hydrogenation reaction, syngas comprisinga mixture of hydrogen and carbon monoxide is contacted with the catalystthereby being converted into liquid and gaseous products, preferablyC₁₀₊ liquid hydrocarbons, with shifting or non-shifting conditions,preferably the latter, wherein little or no water gas shift takes place.This hydrocarbon synthesis (“HCS”) process is generally carried out attemperatures of from about 160° C. to 260° C., pressures of from about 1atm to about 100 atm, preferably from 10 atm to 40 atm, and gas spacevelocities of from about 100 V/Hr/V to about 40,000 V/Hr/V, preferablyfrom about 1,000 V/Hr/V to about 15,000 V/Hr/V. The expression “V/Hr/V”represents the standard volumes of gaseous carbon monoxide and hydrogenmixtures at 25° C. and 1 atm per hour per volume of catalyst,respectively. The molar ratio of hydrogen to carbon monoxide in thesyngas feed is about 2.1:1 for the production of higher hydrocarbons.This ratio may vary to from about 1:1 to 4:1, and preferably is fromabout 1.8:1 to 2.2:1. These reaction conditions are well known and aparticular set of reaction conditions can readily be determined from theparameters given herein. The hydrocarbon-containing products formed inthe process are essentially free of sulfur and nitrogen-containingcontaminants.

[0020] The hydrocarbons produced in a process as described above aretypically upgraded to more valuable products by subjecting all or aportion of the C₅₊ hydrocarbons to fractionation and/or conversion. By“conversion” is meant one or more operations in which the molecularstructure of at least a portion of the hydrocarbon is changed andincludes both non-catalytic processing, e.g. steam cracking, andcatalytic processing, e.g. catalytic cracking, in which the portion, orfraction, is contacted with a suitable catalyst. If hydrogen is presentas a reactant, such process steps are typically referred to ashydroconversion and variously as hydroisomerization, hydrocracking,hydrodewaxing, hydrorefining and the like. More rigorous hydrorefiningis typically referred to as hydrotreating. These reactions are conductedunder conditions well documented in the literature for thehydroconversion of hydrocarbon feeds, including hydrocarbon feeds richin paraffins. Illustrative, but non-limiting, examples of more valuableproducts from such feeds by these processes include synthetic crude oil,liquid fuel, emulsions, purified olefins, solvents, monomers orpolymers, lubricant oils, medicinal oils, waxy hydrocarbons, variousnitrogen- or oxygen-containing products and the like. Examples of liquidfuels includes gasoline, diesel fuel and jet fuel, while lubricating oilincludes automotive oil, jet oil, turbine oil and the like. Industrialoils include well drilling fluids, agricultural oils, heat transfer oilsand the like.

[0021] The syngas utilized in carbon monoxide hydrogenation may beformed by various means known to those of ordinary skill in the art,such as a fluid bed syngas generating unit as is disclosed, for example,in U.S. Pat. Nos. 4,888,131, and 5,160,456. Regardless of the source,syngas typically may contain chemical species, such as hydrogen cyanide,which over time cause deactivation of the catalyst. Other deactivatingchemical species may be formed during the carbon monoxide hydrogenationprocess itself. It is generally recognized that deactivation by thosecontaminants can be reversed by treatment with hydrogen thereby renewingthe catalyst. Certain other causes of catalyst deactivation that cannotbe renewed by hydrogen treatment are often addressed by steam treatmentand/or calcination in air, such treatments being carried out at hightemperatures.

[0022] Regardless of the particular formulation, method of preparation,morphology and size of catalysts, all catalyst will undergo a loss inproductivity and/or selectivity in use. Selectivity may vary with theparticular synthesis, but is generally expressed in terms of the percentof an undesirable substance in the product mixture. For example, methaneis an undesired presence in the Fischer-Tropsch product mixture sincethe object of the process is to form higher molecular weighthydrocarbons. Hence, one method of expressing the worth of a catalyst isits methane selectivity, i.e. the amount of undesirable methane in thereactor mixture.

[0023] Degradation of catalyst productivity may be due to a number ofphenomena including contamination by catalytic poisons, deposition ofcarbonaceous residues, sintering, phase transformation of the metal ormetals in the catalyst and the like. Attrition of the catalystparticulates may also occur and may lead to operational problems inslurry reactors due to the accumulation of fines, particles typicallyless than 10 microns in size. It is commercially significant to improvethe operational reliability of the process and extend the useful life ofa given catalyst prior to its disposal, for example, by means ofregeneration.

[0024] In accordance with the present invention, the HCS process isenhanced by a process whereby the useful life of a used supportedFischer-Tropsch catalyst is materially extended by regeneration. By usedis meant a catalyst that has been exposed to process conditions for thehydrogenation of carbon monoxide. The catalyst is initially treated todecrease its hydrocarbon content. Such processing step is often referredto as “catalyst dewaxing”. This may be carried out by one or more ofseveral techniques. For example, separation may be effected bygravitational or centrifugal separation which allows the hydrocarbon tobe decanted, or removed by filtration, all of which require thehydrocarbons to be in a fluid state. The catalyst may also be treatedwith a solvent or supercritical fluid that effectively weakens theinteraction of the hydrocarbon with the catalyst surface so that theliquid and solid phases can readily be separated in the same manner.This is referred to as solvent washing. Suitable solvents include, forexample, paraffin solvents or naphthas, alcohols, and aromatic solvents.Supercritical fluids include, for example, carbon dioxide, lightparaffins and cyclopentane.

[0025] Another means of decreasing the hydrocarbon content of thecatalyst is to contact it with a hydrogen-containing gas at elevatedtemperatures, i.e. from about 200° C. to 600° C., preferably from 250°C. to 400° C. Typically, the hydrogen pressure would be from atmosphericto about 100 atm, preferably from atmospheric to 30 atm and gas hourlyspace velocities of from about 100 V/Hr/V to about 40,000 V/Hr/V,preferably from about 1,000 V/Hr/V to about 20,000 V/Hr/V, expressed asstandard volumes of the gaseous carbon monoxide and hydrogen mixtures(25° C., 1 atm.) per hour per volume of catalyst, respectively. Thistreatment is advantageous since it also reduces at least a portion ofthe catalytic metal to its metallic state. Alternatively, the catalystmay be contacted with an oxygen-containing gas or steam at elevatedtemperatures to effectively decrease the hydrocarbon content. Due to theoxidation that may take place during this step, it is followed bycontacting with a hydrogen-containing gas at elevated temperatures toreduce at least a portion of the catalytic metal to its metallic state.Solvent washing and hydrogen treatment may also be advantageouslycombined in the subject process.

[0026] Even if another technique is utilized to dewax the catalyst, itis advantageously followed by contacting with a hydrogen-containing gasas discussed above so that at least a portion of the dewaxed catalyst isin its metallic state. Because of the metallic state of at least aportion of the catalyst after decreasing the hydrocarbon content, it isnecessary to recover the catalyst under a non-oxidative atmosphere sincesome catalysts have a tendency to be pyrophoric. By non-oxidative ismeant that the atmosphere need not be a pure inert gas, but may comprisean oxidative gas so long as no substantial oxidation of the catalysttakes place during the recovery thereof. One or a mixture ofart-recognized non-oxidative gases, such as nitrogen, argon and the likemay be utilized to create such atmosphere, with nitrogen beingpreferred. The duration of the dewaxing is adjusted to produce a lowresidual carbon content, for example less than 5 wt. %, preferably lessthan 2 wt. % and typically ranges from 30 minutes to about 8 hours. Ifthe dewaxing step involves or includes contacting the catalyst with asolvent or supercritical fluid, it is preferably dried prior to theimpregnation step.

[0027] In accordance with the present invention, the dewaxed catalyst isimpregnated with a solution of one or more weak organic acids,preferably carboxylic acids, and thereafter oxidized in the presence ofthe impregnating solution. Suitable acids for the subject process arecarboxylic acids having the general formula R—(COOH)_(n) wherein n is1-3 and R represents a cyclic or aliphatic, saturated or unsaturatedmoiety that may be substituted with one or more nitro, amino, hydroxylor alkoxyl groups. Specific examples of suitable acids include, withoutintended limitation, formic acid, acetic acid, citric acid, succinicacid, malonic acid, propionic acid, butyric acid, valeric acid, caproicacid, glutaric acid, adipic acid, lactic acid, benzoic acid, phthalicacid, salicylic acid, ascorbic acid, oxalic acid and the like. Carbonicacid is included within the scope of weak organic acids. Impregnationwith carbonic acid requires that the solution be saturated with carbondioxide and there be sufficient partial pressure thereof in theatmosphere in accordance to sustain its presence in the solution.Preferred weak organic acids include, without intended limitation,acetic acid and citric acid. While combinations of more than one ofthese acids could be utilized, in general it is preferred to utilizethem individually.

[0028] The choice of solvents for the impregnating solution is dependentprimarily on the capacity thereof to solubilize or be miscible with theweak organic acids of the invention. The solvent is preferably water,however, other solvents, e.g. certain organic solvents, may be combinedtherewith provided that they are miscible with water and do notintroduce any known catalytic poison. Mixtures of water and immiscibleorganic solvents can be utilized as well as mixtures of water withsolvents in combination with suitable dispersing or emulsifying agentspresent to form a continuous phase, i.e. an emulsion. Such othersuitable liquids include hydrocarbons, particularly those derived fromthe Fischer-Tropsch synthesis, dense fluids, for example, supercriticalfluids such as liquid phase light, i.e. C₃₋₅, alkanes, cyclopentane andthe like. Preferred mixed liquids include, without any intendedlimitation, water/lower alkanols, water/Fischer-Tropsch products, andwater/alkanols/alkanes.

[0029] The concentration of the weak organic acid in the impregnatingsolution will depend on a number of factors including their solubility,the volume of liquid utilized, the metal loading of the catalyst and thelike. When carbonic acid is utilized as the weak organic acid, theconcentration of the carbonic acid additionally is controlled byadjusting the partial pressure of carbon dioxide in the non-oxidativeatmosphere. In general, the impregnating solution will contain fromabout 1% to about 30%, preferably from about 5% to about 15%, by weightof the subject acid. In a preferred embodiment, the amount of the acidpresent, under any conditions, is less than the amount that would berequired to convert all of the catalyst metals present to theircorresponding salts, e.g. the acetate. The solution of the acid may beprepared by simply diluting or dissolving it in the selected solvent.

[0030] The impregnation will typically be carried out until thesupported catalyst substrate has absorbed a volume of impregnatingsolution equal to at least about 10% of its calculated pore volume,preferably to where conditions of incipient wetness are attained. Byincipient wetness is meant that the substrate catalyst has adsorbed anamount of solution generally equivalent to its calculated pore volume.Pore volume is a discernible quantity that can be measured directly orindirectly by known techniques such as porosimetry. The volume ofimpregnating solution contemplated will vary from 10% to 1,000% of thecalculated pore volume of the catalyst. Preferably, the volume oftreatment solution will be from 30% to 200%, most preferably from about70% to 100% of the calculated pore volume of the catalyst.

[0031] The impregnating solution will remain in contact with thecatalyst for from 1 minute to 24 hours, preferably from about 5 to 120minutes. The time required for the treatment will vary depending onfactors such as the metal loading of the catalyst being treated, thequantity thereof, the composition and volume of the treatment solution,the reactor configuration and the like. The treatment is carried out ata temperature from about 0° C. to about 100° C., preferably from roomtemperature, i.e. 20°-25° C., to about 80° C. The pressure is notparticularly critical and can be from 0.1 to 100 atmospheres, withatmospheric pressure being preferred. It is important, however, that thetreatment be carried out under a non-oxidative atmosphere as definedabove, preferably an inert atmosphere.

[0032] Once the dewaxed, supported catalyst has absorbed the desiredvolume of solution, it undergoes mild oxidation when contacted with anoxidant gas in the presence of the impregnating solution. It has beenfound in accordance with the present invention that the oxidation of thecatalyst is significantly enhanced by the presence of the impregnatingsolution. Without wishing to be bound by any particular theory, it isbelieved that the presence of the acid allows the formation of andenhances the solubility of complexes of the catalyst metal, e.g. Co²⁺.The fact that the solubility of the complexes is enhanced promotes theirdistribution within the pores of the catalyst surface. This dispersing,or redispersing of the catalyst metal enhances the properties of thecatalyst upon activation as will be described below.

[0033] The oxidation of the catalyst is carried out by contact with anoxidant-containing gas. The oxidant-containing gas may be oxygen, air,ozone, nitrogen oxides or other gaseous oxidant, with air or a mixtureof oxygen and an inert gas being preferred. Generally, the concentrationof oxygen in the oxidant gas will be between 10 ppm and 21%, preferablybetween 1% and 21% by volume. Typically, the treatment gas pressurewould be from about 0.1 atm to about 100 atm, preferably atmospheric toabout 10 atm, and the gas hourly space velocities would be from about 10V/Hr/V to about 10,000 V/Hr/V, preferably from about 100 V/Hr/V to about1,000 V/Hr/V, expressed as standard volumes of the gas or gas mixtures(25° C., 1 atm) per hour per volume of catalyst, respectively. Whencarbonic acid is used in the impregnating solution, the oxidantcontaining atmosphere may additionally comprises a suitable amount ofcarbon dioxide.

[0034] The oxidation is typically exothermic and care must be taken tomaintain the temperature below about 100° C., preferably below about 80°C. This is generally carried out by adjusting the concentration of theoxidant in the treatment gas to thereby prevent significant evaporationof the impregnating solution. A gradual increase in the oxidantconcentration in the treatment gas has been found to provide aneffective means of controlling the exotherm. Optionally, incrementalreplacement of the impregnating solution may be carried out during theoxidation. This serves the dual purpose of preventing the catalyst fromdrying out and aiding in controlling the exotherm through the coolingeffect of evaporation.

[0035] The oxidation step is generally carried out until a discerniblechange takes place in the catalyst and/or the reaction environment.Changes in the catalyst will include changes in color. Changes in thereaction atmosphere will include the diminishing of the exotherm. Thisgenerally will require from about 1 to 120 minutes. Once the oxidationis concluded, the catalyst particles are preferably dried, typically ata temperature of from about 50° C. to 150° C., optionally with a gassweep.

[0036] The treated catalyst particles are activated by reduction withhydrogen-containing gas at elevated temperatures, i.e. from about 200°C. to 600° C., preferably from about 250° C. to 400° C. Hydrogen partialpressure during the reduction would range from about 1 to 100atmospheres, preferably from about 1 to 40 atmospheres, and the gashourly space velocities would be from about 100 V/Hr/V to about 40,000V/Hr/V, preferably from about 1,000 V/Hr/V to about 20,000 V/Hr/V,expressed as standard volumes of the gas or gas mixtures (25° C., 1 atm)per hour per volume of catalyst, respectively. The resulting supportedcatalyst particles regenerated in accordance with the present inventionhave been found to have a significant portion of their original activityrestored, both in terms of production of the desired hydrocarbons and inmethane selectivity.

[0037] As an optional step in the subject process, the supportedcatalyst precursor described above is calcined under anoxidant-containing atmosphere prior to the activation step. Theatmosphere is preferably air, but may be an inert atmosphere containinga controlled amount of oxygen, e.g. such as would be produced as aproduct gas stream or a waste gas stream from an air separation plant.Such controlled oxidant-containing atmospheres would contain from 10 ppmto 21% by volume, preferably from about 1% to 21% by volume, oxygen withthe remainder being a non-oxidative gas, preferably an inert gas, suchas nitrogen. The gas flow in the furnace is from about 100 to 10,000,preferably from about 1,000 to 5,000 GSHV. The calcination is carriedout at elevated temperatures, i.e. from about 150° C. to about 600° C.,preferably from about 200° C. to 450° C., for from about 1 to 8 hours,preferably from 1 to about 4 hours. Suitable apparatus for the calciningstep may be a rotary calciner such as described in Perry's chemicalEngineer's Handbook, Seventh Edition, Chapter 12, McGraw-Hill, New York(1997), or a fluidized processor as will be described below or an HCSreactor itself.

[0038] It is a further optional step within the scope of the presentinvention to passivate the treated catalyst after the activation withhydrogen-containing gas has been carried out. The passivation may becarried out by contacting the catalyst with a gas containing carbonmonoxide, or carbon monoxide and hydrogen, under conditions such thatcarbon monoxide does not significantly decompose and is not hydrogenatedto a material degree. Such conditions, for example, would be atemperature below about 150° C., preferably between about 25° C. and100° C., and pressure below about 20 atm, particularly between about 1and 10 atm and the gas hourly space velocities would be from about 1V/Hr/V to about 1,000 V/Hr/V, preferably from about 10 V/Hr/V to about500 V/Hr/V, expressed as standard volumes of the gas or gas mixtures(25° C., 1 atm) per hour per volume of catalyst, respectively. It willbe appreciated that some decomposition or hydrogenation, respectively,of the carbon monoxide may take place regardless of the precautionstaken by the operator. However, it has been found that, typically,significant decomposition/hydrogenation will not take place wherein theconcentration of carbon monoxide or carbon monoxide and hydrogen in thefeed gas does not exceed about 5% by volume. It has been found thatcatalysts that have been passivated in this manner typically exhibithigher initial carbon monoxide hydrogenation activity than similar, butunpassivated, catalysts. Other passivating agents include, for example,traces of oxygen or carbon dioxide. The renewed supported catalystparticles treated in accordance with the present invention have asignificant portion of their original activity and methane selectivityrestored.

[0039] The treatment process in accordance with the present inventionmay be carried out in one or more HCS reactors, in a series of apparatusparticularly adapted to a specific step or steps, or any combinationthereof. For example, the step of decreasing the hydrocarbon content ofa catalyst withdrawn from an HCS reactor may advantageously be carriedout in a mixer-settler vessel as is described in Perry's ChemicalEngineers' Handbook, Seventh Edition, Chapter 18, McGraw-Hill, New York1997. Such a vessel would typically be provided with a heating jacket,agitator and liquid phase withdrawing means. After treatment therein,the catalyst would be withdrawn, typically as a slurry, and be passed toa processor for solvent removal and drying. Alternatively, the step ofdecreasing the hydrocarbon content is carried out in the HCS reactor.

[0040] The processor is a device that can impart mixing and fluidizationto the process. It would be configured to enhance heat transfer, mixingliquid-contacting, and gas solid transfer. Examples of suitableprocessors are gas fluidized beds, vibro-fluidized beds, mechanicalblenders, e.g. double cone, vee, ribbon and the like and mixers such asplow, planetary, paddle and the like. These devices fluidize theprocessed material by passing a gas directly through it, by mechanicalagitation or by a combination of both actions. Processing in such adevice causes the material being treated to attain fluid-like propertiesresulting in intimate contact between each particle and the gas streamthus creating an extremely efficient mass and heat transfer. A devicesthat provides at least mechanical fluidization is particularly preferredsince, although both a slurry and a powder can be made to readily flow,during the drying process from one to the other, the material will passthrough what is termed the “mud stage” where it is extremely difficultto fluidize. Hence, for the drying operation wherein a catalyst is in aslurry, the processor should have at least mechanical and, preferably,both mechanical and gas fluidization.

[0041] A preferred processor for carrying out the subject process is theplow mixer, a device with a jacketed horizontal cylinder with an axialagitator shaft containing several sets of blade or triangular agitators.Such a device will typically also have both gas and liquid inlets andoutlets as well as an inlet and outlet for the solid material beingprocessed. While this is a preferred device, any comparable mixerpossessing the foregoing capabilities could be utilized as well,provided that it has the capacity to continue to fluidize the materialthrough the mud stage of drying. Such a device will also facilitate thesolvent washing that can be part of the process of decreasing thehydrocarbon content of the material as well as the subsequent hydrogentreatment at elevated temperatures. This is a preferred method ofdecreasing hydrocarbon content since it permits recovery of the wax, animportant consideration.

[0042] The next step, treatment with the impregnation solution asdescribed above can likewise be carried out in a mechanical mixer, suchas a plow mixer for the reasons stated above. The mixer is advantageousin that the liquid may be added while the material is in a fluidizedcondition. Because the mixer has inlet and outlet means for gas, whenthe material has been impregnated to the desired degree, the subsequentoxidation with a gaseous oxidant may be affected therein as well. At thecompletion of the low temperature oxidation step, as indicated by thecessation of the exotherm, the material may remain in the processor, ormay be removed for further processing, for example, the removal offines, drying and calcination steps discussed above. All of theseoperations may be carried out in the processor if desired. However,suitable devices for removal of fines from dry particulate solids, forexample by sieving, elutriation from fluidized beds, gas classificationand the like, are described in Perry's Chemical Engineers' Handbook,Seventh Edition, Chapters 17, 19 and 20, McGraw-Hill, New York 1997.

[0043] The final activation of the material to form an active catalystcan be carried out in a fluidized processor as described above. A largervariety of devices may be utilized for this step, however, since thematerial does not pass through a mud phase, hence gas fluidizers can beutilized for the excellent solid-gas contact they provide. For the samereason, a gas fluidizer may be utilized for the optional passivationstep described above as, again, the material does not transcend througha mud phase. It can be appreciated, that a series of varied devices canbe utilized to carry out the process of the present invention, which maybe advantageous for large scale operations. However, as described above,it is also possible to carry out the entire process of regeneration ofthe used supported catalyst in a mechanical fluidizer having thecapabilities of solid, gas and liquid transfer.

[0044] It is understood that various other embodiments and modificationsin the practice of the invention will be apparent to, and can be readilymade by, those of ordinary skill in the art without departing form thescope and spirit of the invention as described above. Accordingly, it isnot intended that the scope of the claims appended hereto be limited tothe exact description set forth above, but rather that the claims beconstrued as encompassing all of the features of patentable novelty thatreside in the present invention, including all the features andembodiments that would be treated as equivalents thereof by thoseskilled in the art to which the invention pertains. The invention isfurther described with reference to the following experimental work.

EXAMPLE 1 Solvent Dewaxing Of Deactivated Catalyst

[0045] Chunks of cobalt-based catalyst on a titania support in wax thatwere removed from a Fischer-Tropsch reactor in operation for over twohundred days weighing 83 grams were placed in a beaker and covered withtoluene. The mixture was heated to 85-90° C. and stirred by hand. Thechunks broke apart during the heating/stirring. After 5 minutes, thetoluene/wax solution was decanted, fresh toluene added and the processrepeated twice more. After the third decanting, the remainingtoluene/catalyst slurry was transferred to a Buchner funnel and filteredhot. Hot toluene was poured onto the filter cake three times and drawnthrough the filter cake by applied vacuum. The filter cake was dried onthe funnel by the application of vacuum to yield 58.4 grams ofnon-pyrophoric catalyst. The catalyst contained substantial amounts ofreduced cobalt as indicated by its high magnetic permeability. Thecatalyst was easily moved with a small permanent magnet. A second samplewas prepared in a like manner with the additional step of being airdried overnight after being dried on the funnel. Its characteristicswere the same.

EXAMPLE 2 Hydrogen Dewaxing of Solvent Dewaxed Catalysts

[0046] Catalyst prepared in accordance with Example 1 (120 g), catalystwas charged to a fixed bed reactor, which was purged with nitrogen for30 minutes. The reactor temperature was raised to 100° C. and the gasflow changed to 10% hydrogen in nitrogen. The temperature was thenraised to 288° C. and the gas flow established at 450 sccm of purehydrogen. The catalyst was maintained for three hours to completeremoval of organic compounds and to reduce the metal components. Thereactor was cooled and the gas flow changed to nitrogen when it droppedbelow 100° C. When the reactor had cooled to ambient temperature, thecatalyst was discharged under a nitrogen atmosphere, yield 118.4 g ofreduced catalyst. The catalyst contained substantial amount of metalliccobalt and was moved easily with a permanent magnet.

EXAMPLE 3 Testing of Catalyst from Example 1

[0047] The catalyst from Example 1 was tested in a laboratory fixed bedreactor. The catalyst (2 mL, 2.80 g) was mixed with a quartz diluent (4mL, 6.54 g) and placed into a 1 cm inside diameter tubular reactor. Thecatalyst bed was held in place with a plug of glass wool. A multi-pointthermocouple was inserted into the bed to monitor temperatures. Thecatalyst was initially reduced by hydrogen at 375° C., 19.7 atm and 315sccm of hydrogen over two hours. The catalyst was cooled to 177° C.,19.7 atm under a flow of 10 sccm Argon and 260 sccm hydrogen. Aftercooling, the feed composition was changed to 12 sccm argon, 134 sccmhydrogen and 94 sccm of a carbon monoxide/carbon dioxide blend, giving anominal feed composition of 56.0% H₂, 11.6% CO₂, 4.9% Ar and 27.5% CO,wherein the percentages are given as mole percents. The reactor was thenheated at 2.8° C./hour to 199° C. and held at temperature for 24 hours.The reactor was then heated at 2.8° C./hour to 213° C. and held attemperature for the remainder of the test.

[0048] At this temperature, the CO conversion was 27.3% and the methaneselectivity was 7.6%. After 24 hours under these conditions, the COconversion was 24.3% and the methane selectivity was 7.6%. Methaneselectivity is defined as the carbon in the methane produced as afraction of the carbon in the converted carbon monoxide.

EXAMPLE 4 Air Regeneration of Solvent Dewaxed Catalyst

[0049] Thirty grams of catalyst from Example 1 were placed in a ceramicdish and calcined in air at 300° C. for two hours. The calcined catalystwas recovered as a dry dark gray powder. The calcined catalyst wastested for catalytic activity according the procedure described inexample 3. The CO conversion was 55.0% and the methane selectivity was10.9%. After 24 hours under these conditions, the CO conversion was52.4% and the methane selectivity was 10.5%. This example shows thatcatalytic activity can be recovered by air calcination of thedeactivated catalyst

EXAMPLE 5 Aqueous Low Temperature Oxidized Catalyst Utilizing Water andAir as Oxidant

[0050] The catalyst (3.2 g), prepared according to example 2, was placedin a 2 oz. bottle under a nitrogen atmosphere and 0.82 mL of water addedto incipient wetness. The impregnated catalyst was then placed under anair atmosphere for an hour, after which it was dried in a vacuum oven at80° C. and subsequently calcined in air at 300° C. for two hours. Thecatalyst was tested for catalytic activity according to the proceduredescribed in Example 3. The CO conversion was 55.1% and the methaneselectivity was 9.5%. After 24 hours under these conditions, the COconversion was 52.8% and the methane selectivity was 9.2%.

[0051] This example shows that the activity recovery by low temperatureair oxidation in presence of liquid water is essentially equivalent toair calcination.

EXAMPLE 6 Acetic Acid Assisted Aqueous Low Temperature Air Oxidation ofHydrogen Dewaxed Catalyst

[0052] A solution was prepared by adding 7.21 grams of glacial aceticacid to deionized water and diluting to a volume of 50 ml. 2.75 grams ofthe acetic acid solution were added to ten grams of the catalyst fromExample 2 under inert conditions. The sample was then placed under anair atmosphere and mixed vigorously. A mild exotherm occurred whichsubsided after several minutes. After an additional 2 hours in air, thesample was a greenish-gray color. The sample was dried at 100° C. for 1hr and then calcined at 300° C. for 2 hours. 10.11 grams of a dark graypowder were recovered. The catalyst was tested for catalytic activityaccording the procedure described in example 3. The CO conversion was82.1% and the methane selectivity was 7.1%. After 1 day at thiscondition, the CO conversion was 78.1% and the methane selectivity was7.3%.

EXAMPLE 7 Formic Acid Assisted Aqueous Low Temperature Air Oxidation ofHydrogen Dewaxed Catalyst

[0053] A solution was prepared by adding 5.52 grams of formic acid todeionized water and diluting to a volume of 50 ml. 2.80 grams of theformic acid solution were added to ten grams of the catalyst fromExample 2 under inert conditions. The sample was then placed under anair atmosphere and mixed vigorously, the resulting mild exothermsubsiding after several minutes. After an additional 2 hours in air, thesample was greenish-gray. The sample was dried at 100° C. for 1 hr andthen calcined at 300° C. for 2 hours to yield 10.4 grams of a dark graypowder.

[0054] The catalyst was tested for catalytic activity according theprocedure described in example 3. The CO conversion was 72.6% and themethane selectivity was 7.1%. After 1 day at this condition, the COconversion was 69.4% and the methane selectivity was 6.9%.

EXAMPLE 8 Citric Acid Assisted Aqueous Low Temperature Air Oxidation ofHydrogen Dewaxed Catalyst

[0055] A solution was prepared by adding 23.05 grams of citric acid todeionized water and diluting to a volume of 50 ml. 2.77 grams of thecitric acid solution were added to ten grams of the catalyst fromExample 2 under inert conditions. The sample was then placed under anair atmosphere and mixed vigorously. A mild exotherm occurred whichsubsided after several minutes. After an additional 2 hours in air, thesample was a light gray color. The sample was dried at 100° C. for 1 hrand then calcined at 300° C. for 2 hours. Approximately 10 grams of adark gray powder were recovered. The catalyst was tested for catalyticactivity according the procedure described in example 3. The COconversion was 64.1% and the CH₄ selectivity was 7.1%. After 1 day atthis condition, the CO conversion was 60.9% and the methane selectivitywas 7.1%.

EXAMPLE 9 Calcination of Hydrogen Dewaxed Catalyst

[0056] Thirty grams of catalyst from Example 1 were placed in a ceramicdish and calcined in air at 300° C. for two hours. The material wasrecovered as a dry dark gray powder.

EXAMPLE 10 Acetic Acid Assisted Aqueous Low Temperature Air Oxidation ofCalcined Dewaxed Catalyst

[0057] A solution was prepared by adding 7.21 grams of glacial aceticacid to is deionized water and diluting to a volume of 50 ml. 2.01 gramsof the solution were added to 9.07 grams of the catalyst from Example 9.The sample was then placed under an air atmosphere and mixed vigorously.No exotherm occurred. After an additional 2 hours in air, the sample wasa gray in color. The sample was dried at 100° C. for 1 hr and thencalcined at 300° C. for 2 hours to yield 9.04 grams of a dark graypowder. Testing of the catalyst according the procedure described inExample 3 showed the CO conversion was 48.1% and the methane selectivitywas 7.35%.

EXAMPLE 11 Carbonic Acid Assisted Aqueous Low Temperature Air Oxidationof Hydrogen Dewaxed Catalyst

[0058] A solution was prepared by dissolving Dry Ice in deionized wateruntil the pH of the solution quit decreasing. A pH around 4 from 6.8 wasachieved. 2.70 grams of the carbonic acid solution were added to tengrams of the catalyst from Example 2 under inert conditions. The samplewas then placed under an air atmosphere and mixed vigorously. A mildexotherm occurred which subsided after several minutes. After anadditional 4 hours in air, the sample was a gray color. The sample wasdried at 100° C. for 1 hr and then calcined at 300° C. for 2 hours. 9.4Grams of a dark gray powder were recovered.

[0059] The catalyst was tested for catalytic activity according theprocedure described in example 3. The CO conversion was 63% and themethane selectivity was 6.8%. After 1 day at this condition, the COconversion was 60% and the methane selectivity was 6.6%.

What is claimed is:
 1. A process for the regeneration of used, supportedcatalyst comprising one or more members selected from the groupconsisting of Co, Ni, Cu, Ru, Rh, Re, Pd, Pt, Os and Ir, the processcomprising the following steps: a) decreasing the hydrocarbon content;b) impregnating under a non-oxidative atmosphere with a solution of atleast one weak organic acid; c) oxidizing with a gaseous oxidant in thepresence of the impregnating solution; and d) reducing with ahydrogen-containing gas at elevated temperatures thereby forming anactive catalyst.
 2. A process in accordance with claim 1, wherein thehydrocarbon content of the used catalyst is decreased by one of thefollowing steps: contacting with a hydrogen-containing gas at elevatedtemperatures; contacting with a solvent or supercritical fluid;contacting with a solvent or supercritical fluid and then contactingwith a hydrogen-containing gas at elevated temperatures; contacting thecatalyst with an oxygen-containing gas or steam at elevated temperaturesand then contacting it with a hydrogen-containing gas at elevatedtemperatures; and contacting with a solvent or supercritical fluid,contacting with an oxygen-containing gas or steam at elevatedtemperatures and then contacting with a hydrogen-containing gas atelevated temperatures.
 3. A process in accordance with claim 1, whereinstep a) additionally includes the step of drying the catalyst.
 4. Aprocess in accordance with claim 1, wherein said at least one weakorganic acid is a carboxylic acid having the general formulaR—(COOH)_(n) wherein n is 1-3 and R represents a cyclic or aliphatic,saturated or unsaturated moiety that may be substituted with one or morenitro, amino, hydroxyl or alkoxyl groups and the amount in theimpregnating solution in step b) is less than an amount that would berequired to convert substantially all of said at least one catalystmetal to its corresponding salts.
 5. A process in accordance with claim4, wherein said at least one weak organic acid in the impregnatingsolution in step b) is selected from the group consisting of formicacid, acetic acid, citric acid, succinic acid and malonic acid.
 6. Aprocess in accordance with claim 5, wherein said at least one weakorganic acid is acetic acid.
 7. A process in accordance with claim 1,wherein the amount of said impregnating solution utilized in step b) isfrom about 10% to 1000% of the calculated pore volume of the catalyst.8. A process in accordance with claim 7, wherein the amount of saidimpregnating solution utilized in step b) is from about 30% to 200% ofthe calculated pore volume of the catalyst.
 9. A process in accordancewith claim 1, wherein step c) additionally includes the step of dryingthe catalyst.
 10. A process in accordance with claim 1, wherein thegaseous oxidant in step c) is selected from the group consisting ofoxygen, air, ozone and nitrogen oxides.
 11. A process in accordance withclaim 1, wherein the temperature during the oxidation in step c) ismaintained below about 100° C.
 12. A process in accordance with claim 1,wherein the reduction in step d) is with hydrogen-containing gas at atemperature of from about 200° C. to 600° C.
 13. A process in accordancewith claim 1 additionally including the step of calcining under anoxidant-containing atmosphere between steps c) and d).
 14. A process inaccordance with claim 13, wherein the oxidant-containing atmosphere isair.
 15. A process in accordance with claim 13, wherein theoxidant-containing atmosphere contains from about 10 ppm to about 21% byvolume of oxygen with the remainder being a non-oxidative gas.
 16. Aprocess in accordance with claim 1 additionally including the step ofpassivating the catalyst formed in step d) by: treatment with a carbonmonoxide-containing gas under conditions such that the carbon monoxideis not significantly decomposed; or treatment with a gas containingcarbon monoxide and hydrogen under conditions such that the carbonmonoxide is not significantly hydrogenated.
 17. A process in accordancewith claim 1, wherein said catalyst comprises cobalt.
 18. A process forthe treatment of a used, supported catalyst comprising one or moremembers selected from the group consisting of Co, Ni, Cu, Ru, Rh, Re,Pd, Pt, Os and Ir, the process comprising the following steps: a)decreasing the hydrocarbon content by one of the following steps:; i)contacting with a hydrogen-containing gas at elevated temperatures; ii)contacting with a solvent or supercritical fluid; iii) contacting with asolvent or supercritical fluid and then contacting with ahydrogen-containing gas at elevated temperatures; iv) contacting thecatalyst with an oxygen-containing gas or steam at elevated temperaturesand then contacting it with a hydrogen-containing gas at elevatedtemperatures; and v) contacting with a solvent or supercritical fluid,contacting with an oxygen-containing gas or steam at elevatedtemperatures and then contacting with a hydrogen-containing gas atelevated temperatures; b) impregnating under a non-oxidative atmospherewith a solution of at least one weak organic acid or carbonic acid; c)oxidizing with a gaseous oxidant in the presence of the impregnatingsolution; and d) reducing with a hydrogen-containing gas at elevatedtemperatures thereby forming an active catalyst.
 19. A supported metalcatalyst for the catalytic hydrogenation of carbon monoxide comprisingone or more members selected from the group consisting of Co, Ni, Cu,Ru, Rh, Re, Pd, Pt, Os and Ir, said catalyst being formed from a usedcatalyst by a process comprising: a) decreasing the hydrocarbon content;b) impregnating under a non-oxidative atmosphere with a solution of atleast one weak organic acid; c) oxidizing with a gaseous oxidant in thepresence of the impregnating solution; and d) reducing with ahydrogen-containing gas at elevated temperatures thereby forming anactive catalyst.
 20. A supported metal catalyst for the catalytichydrogenation of carbon monoxide comprising one or more members selectedfrom the group consisting of Co, Ni, Cu, Ru, Rh, Re, Pd, Pt, Os and Ir,said catalyst being formed from a used catalyst by a process comprisingthe following steps: a) decreasing the hydrocarbon content by one of thefollowing steps:; i) contacting with a hydrogen-containing gas atelevated temperatures; ii) contacting with a solvent or supercriticalfluid; iii) contacting with a solvent or supercritical fluid and thencontacting with a hydrogen-containing gas at elevated temperatures; iv)contacting the catalyst with an oxygen-containing gas or steam atelevated temperatures and then contacting it with a hydrogen-containinggas at elevated temperatures; and v) contacting with a solvent orsupercritical fluid, contacting with an oxygen-containing gas or steamat elevated temperatures and then contacting with a hydrogen-containinggas at elevated temperatures; b) impregnating under a non-oxidativeatmosphere with a solution of at least one weak organic acid; c)oxidizing with a gaseous oxidant in the presence of the impregnatingsolution; and d) reducing with a hydrogen-containing gas at elevatedtemperatures thereby forming an active catalyst.
 21. A process forproducing C₁₀₊ hydrocarbons by the hydrogenation of carbon monoxide byreaction with hydrogen at reaction conditions in the presence of arenewed catalyst according to claim
 19. 22. A process in accordance withclaim 21, wherein at least a portion of the hydrocarbons formed areupgraded to more valuable products by at least one of fractionation andconversion operations.
 23. A process for producing C₁₀₊ hydrocarbons bythe hydrogenation of carbon monoxide by reaction with hydrogen atreaction conditions in the presence of a renewed catalyst according toclaim
 20. 24. A process in accordance with claim 23, wherein at least aportion of the hydrocarbons formed are upgraded to more valuableproducts by at least one of fractionation and conversion operations.